What determines the number of juvenile instars in the tropical grasshopper Cornops aquaticum (Leptysminae: Acrididae: Orthoptera)?

Cornops aquaticum (Bruner) is host specific on Eichhornia spp. and Pontederia spp. (Pontederiacae). Its present distribution ranges from Mexico to Argentina. The number of juvenile instars (5-7) apparently mirrors the photoperiod and temperature pulses of different climatical conditions in the respective geographical regions. Based on life-history data, three working hypotheses are proposed for forthcoming studies. These will test whether the varying number of juvenile instars represents a phenotypic plasticity of a single genotype or an adaptation that is genetically fixed, due to an evolutionary relationship of the host with its host-plant.